Authors:Víctor Cervantes, Ana Santana, Georgina Guilera, and Juana Gómez-Benito
Development of research methods requires a systematic review of their status. This study focuses on the use of Hierarchical
Linear Modeling methods in psychiatric research. Evaluation includes 207 documents published until 2007, included and indexed
in the ISI Web of Knowledge databases; analyses focuses on the 194 articles in the sample. Bibliometric methods are used to
describe the publications patterns. Results indicate a growing interest in applying the models and an establishment of methods
after 2000. Both Lotka’s and Bradford’s distributions are adjusted to the data.
observation period in this case. The ratio of people appointed to professorial positions from the group of alma maters immediately below the new organization is increasing year on year (reference P value = 0.03).
Authors:Bernd Spangenberg, Peter Post, and Siegfried Ebel
High performance thin layer chromatography (HPTLC) is a frequently used separation technique which works well for quantification of caffeine and quinine in beverages. Competing separation techniques, e.g. high-performance liquid chromatography (HPLC) or gas chromatography (GC), are not suitable for sugar-containing samples, because these methods need special pretreatment by the analyst. In HPTLC, however, it is possible to separate ‘dirty’ samples without time-consuming pretreatment, because disposable HPTLC plates are used. A convenient method for quantification of caffeine and quinine in beverages, without sample pretreatment, is presented below. The basic theory of in-situ quantification in HPTLC by use of remitted light is introduced and discussed. Several linearization models are discussed.A home-made diode-array scanner has been used for quantification; this, for the first time, enables simultaneous measurements at different wavelengths. The new scanner also enables fluorescence evaluation without further equipment. Simultaneous recording at different wavelengths improves the accuracy and reliability of HPTLC analysis. These aspects result in substantial improvement of in-situ quantitative densitometric analysis and enable quantification of compounds in beverages.
Six oligomers of -aminocaproic acid (ACA) from dimer (K2) to heptamer (K7), gamma-irradiated in an oxygen-free atmosphere, were investigated by the EPR method. The oligomers were synthesized and irradiated with60Co gamma-rays in the dose range from 0 to 6.5 kGy. The formation of –CH2–CONH–CH–CH2– radical was established. The quantitative determinations of total concentrations of spins were carried out. On the basis of the present and earlier results, the competition of the reactions of detachment of hydrogen and of breaking of –CONH– bond is discussed. The particular resistance of amide bond in dimer seems to be confirmed by the measurements of kinetics of radical decay. The mass spectrometry of gamma-unirradiated ACA and ACA oligomers K2-K4 was carried out. The results indicate a minute contribution of ionic processes in the radiolysis of ACA oligomers in solid phase.
Authors:H. Bu, X. Chen, Y. Wang, X. Xu, K. Liu, and G. Du
In this paper, 633 species (involving 10 classes, 48 families, 205 genera) collected from the alpine meadow on the eastern Qinghai-Tibet plateau were studied. We tested potential factors affecting variation in mean germination time (MGT), i.e., plant traits (adult longevity, dispersal mode and seed size) or phylogeny, to evaluate if these factors were independent or they had interaction. Nested ANOVA showed that taxonomic membership accounted for the majority of MGT variation (70%), and in the generalized linear model, family membership could explain independently the largest proportion of MGT variation (29%). The strong taxonomic effect suggests that MGT variation within taxonomic membership is constrained. The other plant traits could also explain MGT variation independently (1% by adult longevity and dispersal mode, respectively, and 2% by seed size). Thus, the phylogeny was an important constraint to maintain the stability of species, and we could simplify the question if we regarded the phylogeny as an individual factor, but we could not negate the adaptive significance of the relationship between other plant traits and seed MGT. In addition, a large percentage of the variance remained unexplained by our model, thus important selective factors or parameters may have been left out of this analysis. We suggest that other possible correlates may exist between seed germination time and additional ecological factors (for example, altitude, habitat and post-dispersal predation) or phylogenetic related morphological and physiological seed attributes (e.g., endosperm mass) that were not evaluated in this study.
We study probability distributions on all possible complete matchings in a complete bipartite graph, where the vertices in
both sets admit a linear order. We define a family of distributions, and give its equivalent implicit and explicit (parametric)
description: it is characterized implicitly by a collection of interesting conditional independence statements, or explicitly
by the property that the distributions belonging to the family factorize into factors which depend on “local” properties of
the matching. We also calculate the number of free parameters in this family.
perfectly flexible, i.e. it has no bending stiffness. The nonlinear model can be derived by the help of truss elements which can transfer only axial force [ 10 ] and perform 2D motions. The linearmodel practically is a taut string [ 11 ], which is
Authors:Farhad Gharagheizi, Mohammad Hossein Keshavarz, and Mehdi Sattari
multivariate linearmodel has three parameters because increase in the number of molecular descriptors has no significant effect on the accuracy of the best model. This equation and its statistical parameters are presented as:
where s is residual mean
sustainability mainly relies on the linearmodel specifications. However, in some cases the relationship between exports and imports can hardly be established using the linear specification forms. Furthermore, in other cases a linear relationship between exports